AC 33-2A 5 June 1972 Therefore, retesting of engines with all recent design changes appears desirable when incorporating a design change or group of design changes in order to assess these effects and may include development, endurance, vibration, and fatigue testing. Submittal of descriptíve data is needed for FAA approval or for DER approval when appropriately authorized.
C. Replacement or Modification Parts Produced by Other Than the Engine Type Certificate Holder. Design approvals of these parts may be granted as either identical parts to those in the engine type design, or as modifications to the type design. Acceptable means of compliance for processing these replacement parts in complying with FAR, Section 21.303, are contained in Advisory Circular
21.303-1. When the applicant desires to substantiate parts embodying extensive new design, complete type design data are required in the manner applicable to new applications for type certificates as prescribed in FAR, Section 21.19. When the applicant desires to substantiate parts embodying major type design changes not great enough to require a i new application for type certificate, a supplemental type certificate as prescribed in FAR, Section 21.113, may be issued.
18. RESERVED.
19. PROCESSING CHANGES IN TYPE DESIGN. (FAR, Part 21, Subparts D and E)
a. Minor Changes. Section 21.95 of the FAR applies to the approval of minor changes in type design. Such changes normally require only a drawing comparison to substantiate their airworthiness.
Typical examples of minor changes are included in the list which follows this paragraph. These changes may be approved by the applicant's appropriately authorized DER. An acceptable method of handling these changes includes submitting to FAA the engineering design change notices, where necessary to fully describe the changes, and detail drawings showing the changes. Intervals between submittal of each new change or group of changes should not exceed six months. Consideration should be given to the possibility that, while certain design changes may well be considered minor when evaluated singly, the cumulative influence of numbers of such changes may have an adverse effect and may have to be evaluated as major changes. The following is a list of typical minor changes:
(1) Slight variations in clearances.
(2) Reasonable increase in radius of fillets.
(3) Increase in thickness where the design permits it without adverse effects.
5 June 1972 AC 33-2A
(4) Change to equivalent or improved material in minor parts.
(5) Improvements in heat treatments of parts, without reducing elongation of parts subjected to high stress.
(6) Small changes in the design of unimportant parts of the engine.
Major Changes. Section 21.97 of the FAR applies to the approval of major changes in the type design. To substantiate major changes to a certificated engine, substantiating data must be submitted.
Typical examples of major changes are included in the list which follows this paragraph. Acceptable substantiating data include at least technical data and drawings, together with reports oi tests, when applicable. As provided in FAR, Part 21, Subpart D, a type certificate holder may apply for amendment of the original type certificate for major changes. As provided in FAR, Part 21, Subpart E, applicants other than the type certificate holder may apply for a supplemental type certificate when appropriate for major changes. The applicant should meet at least the minimum miness gen chantantiaco airworthiness standards applicable to the original engine when qualifying design changes. When an unsafe condition has developed, special substantiation may be required to demonstrate that the unsafe condition has been overcome by the proposed type design change. Changes that will contribute to improved safety are often developed as a result of service experience and may be approved as constituting the current type design standard in compliance with FAR, Section 21.99(b). Major changes may be recommended for approval by the type certificate holder's appropriately designated DER, but may not be introduced into service use until approved by the FAA Regional Engineering Office.
The following is a list of typical major changes:
(1) A change of either compression ratio or supercharger gear ratio.
Establishing the eligibility of engines for either an increase in the oil inlet temperature, rating, inlet or exhaust gas temperatures, cylinder base or head temperatures, or speed.
(3) A change in the material or design of highly stressed parts, either rotating, reciprocating, or non-rotating, likely to affect adversely the airworthiness of such parts.
(4) A change involving method of clamping or attaching rotating, reciprocating, or non-rotating parts.
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AC 33-2A 5 June 1972
(5) Any change of parts or materials from which a conclusive decision cannot be made concerning the integrity of the engine from reliability, durability, and dependability standpoints.
Type Design Data Lists. A drawing list as discussed in paragraph 9c(1) (b) is recommended reflecting both major and minor changes, to be provided at intervals not exceeding six months to cover each certificated engine model which has a currently effective type certificate.
20. RESERVED.
21. IDENTIFICATION PLATE. (FAR, Parts 33 and 45, Subpart B.)
a. General. An acceptable method of complying with the fireproof and location requirements of FAR, Section 45.11(a), is to meet the following conditions:
(1) The data thereon is legible after the application of a 2,000° F. flame for 15 minutes.
(2) The plate is located in an accessible place on the engine for easy viewing and is not expected to be easily defaced or dislodged.
b. Identification Data. The type of information to be included on the identification plate is prescribed in FAR, Section 45.13.
Identification Plate Attachment. Compliance with FAR, Sections
33.13 and 33.19, must be shown in that the means of attaching the identification plate will not cause cracks, induce fluid leaks, or be susceptible to dislodgement within the interior of the engine, or otherwise adversely affect the engine durability or introduce design features shown to be hazardous or unreliable.
22. RESERVED.
23. INSTRUCTION MANUAL. (FAR, Section 33.5) The applicant's manual or manuals should contain at least the following:
a. An engine description covering its major components, al.
accessories, its fuel, lubrication, ignition, cooling, and control systems, and principles of operation. Appropriate charts, diagrams, and illustrations are recommended.
b. Installation criteria including pertinent engineering data and limits for parameters affecting the installed engine and general recommended installation practices to assist in achieving compatibility of engine and installation.
Chap 1 Page 24 Par 19
5 June 1972 AC 33-2A Operating instructions including specified fuels, oil, and hydraulic fluids, starting and operation under normal and extreme characteristics including operating limits, engine ambient and engine temperatures and altitudes. Engine operating os ratn die settin Engine per formance acceleration characteristics from idle settings with handling characteristics on the ground and in flight. Engine performance characteristics data to provide both aircraft applicant and operator with the necessary data for determining output levels at all applicable flight altitudes.
d. Maintenance, servicing, and overhaul instructions including:
(1) Methods of rectifying typical faults.
(2) Recommended inspection instructions and periods at which the engine, its components and accessories should be inspected, cleaned, lubricated, adjusted, and tested when used by general aviation operators. Recommendations for initial inspection periods for other operators may be supplied in a manner applicable to air carrier uses.
(3) Recommended periods at which overhauls and replacements should be made by the general aviation operators.
Recommendations for initial overhauls and replacements for other operators may be supplied in a manner applicable to air carrier uses. Include life limits for all affected components.
(4) A list of any special tools and equipment required to perform inspections, assembly, and disassembly together with details of their use.
(5) The order and method of dismantling.
(6) The order and method of reassembly.
(7) Recommended methods of testing after overhaul or maintenance.
(8) Table of fits, clearances, and torque limits for use in assembly and checking.
24. RESERVED.
Chap Par 23 Page 25
AC 33-2A 5 June 1972 ENGINE RATINGS AND OPERATING LIMITATIONS. (FAR, Section 33.7) Acceptable means of complying with the requircments of FAR, Section 33.7, for establishing engine ratings and operating limitations are as follows:
a. Tests.
(1) Specific block tests are conducted to establish the various rated powers and thrusts and the maximum and minimum operating limitations. The effects of altitude on engine ratings and operating limitations should be determined acceptably. This is usually accomplished by means of altitude chamber testing or flight testing or simulated altitude tests. Analytical data have been acceptable occasionally.
(2) The limiting maximum ratings, speeds, and temperatures should be qualified by operation as indicated in the 150-hour FAA endurance test. Other limitations may be qualified by testing in which the limiting value may be the average attained for appropriate durations.
(3) Special or additional tests may be necessary at times to qualify some limitations for either complex engines, such as turbine engines with several rotor systems when limiting test conditions cannot be easily maintained for all rotors simultaneously, or where limits for components may be tested separately on rig tests.
b. Ratings and Limitations.
Rated engine powers and thrusts are usually established on the basis of engine operation on a test stand in its normal operating configuration, but usually with at least a test stand inlet in place of the aircraft installation hardware.
Ratings are included on the engine type certificate data sheet.
(2) Any operating limitations that may be considered by the applicant to affect flight safety, if exceeded, are to be noted in the model description and should include such items
(a) Maximum engine speeds.
Temperatures. For reciprocating engines, this nay include maximum limits for cylinder heads and barrels, coolant, lubricant, fuel, inlet air or supercharger outlet air, and designated essential engine accessories.
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AC 33-2A 5 June 1972 Minimum limits may apply to lubricants. For turbine engines, maximum limits may include limits for inlet air, bleed air, exhaust or turbine gas, lubricant, fuel, hydraulic fluids, and designated external points such as to lubricants, fuel, and hydraulic fluids. It is recommended that turbine gas temperature operating limits should encompass allowances to ensure that substantiated turbine inlet temperature will not be exceeded when the engine is operated to the speed and power limits under normal flight conditions. If the gas temperature limits vary with changing flight conditions, they should be such as to permit operation within safe limits using average pilot attention and skill.
Maximum and minimum pressures. These may include limits on fuel, lubricants, hydraulic fluids, pneumatic systems, manifold pressures and exhaust back pressure for reciprocating engines, inlet and exhaust pressures and bleed air pressure for turbine engines.
Limitations on the type and quality of fuels, lubricants, and, when used, hydraulic oils. The essential limitations are normally identified in the material specification which identifies the fluid. Any optional additives which have been approved for use with these fluids should be designated by the applicant and instructions for their use included.
Accessory drive limit loads, including overhang moment, torque or power and vibratory loads, for aircraft accessories drive and mounting provisions on the engine.
Note: These limitations will be included on the engine IC data sheet with other data necessary for operation and installation in aircraft covered in installation or operation instructions.
26. RESERVED •
27. SELECTION OF ENGINE POWER AND THRUSI RATINGS. (FAR, Section 33.8.).
The objective of this requirement is to establish on a uniform basis the power or thrust ratings which new engines and engines restored to new condition are required to produce.
These ratings are used in establishing aircraft performance for which consistent minimum performance is desired.
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5 June 1972 AC 33-2A
b. Applicability. for engines of new type design whose applications for IC were This requirement, effective April 3, 1967, is submitted on or after this date. Also included are engines for which type design changes are proposed and the Administrator finds that a new application for type certificate is necessary because of extensive changes in accordance with FAR, Section 21.19.
c. Establishment of Ratings. and are established by the FAA block tests. Ratings are based on The ratings are selected by the applicant standard atmospheric conditions using test methods which will provide accuracies comparable to good industry practice. The applicant's experience on the calibrated output of a number of engines of both the applicable new model and of engines of closely similar design characteristics should be reviewed to evaluate the range of output expected in all other engines of that type. The selected ratings should be consistent with the output of the lowest output engíne anticipated.
CHAPTER 2. Reserved chappi par Page 28
5 June 1972 AC 33-2A Appendix 1 APPENDIX 1. TURBINE ENGINE MODEL DESCRIPTION The model description is for the purpose of establishing those features of the engine that are involved in the certification and safe operation of the engine. The applicant should submit, where applicable, the following information plus any additional information which, in his opinion, is essential to the certification and safe operation of the engine:
a. Applicant's name.
b. Engine model, cycle used, number of rotors, stages and their arrangement.
c. Performance ratings as defined in FAR, Part 1. (See Table 1.)
d. Estimated engine performance graphs consistent with the ratings.
e. Maximum structural loading envelope, including mounting attachments and allowable loads.
f. Maximum time engine may be operated under negative and zero "g" conditions.
g. Maximum permissible temperature limits and cooling criteria for engine components and accessories.
(1) Type and location of thermocouple to use for çooling test as applicable.
(2) Description of temperature sensing provisions if incorporated.
h. Bleed air temperature, pressure, and flow limits, and the extent and nature of contaminants which may be present and are possibly harmful if breathed.
i. Maximum permissible air inlet duct attachment loads.
(1) Shear loads.
(2) Loads normal to mounting surfaces.
(3) Overhung moment.
j. Inlet air requirements.
(1) Maximum limits of radial and circumferential distortion.
(2) Maximum limits of velocity distribution.
AC 33-2A 5 June 1972 Appendix 1
(3) Correction factors for inlet pressure losses.
k. Lubrication system.
(1) Oil grade, type, and specification.
(2) Oil consumption rate (normal and maximum).
(3) Oil inlet pressure limits.
(4) Oil system vent pressure limits.
(5) Oil inlet and scavenge temperature limits.
(6) Inlet oil flow rate.
(7) Usable oil capacity, if oil tank is part of engine.
(8) Maximum heat rejection to oil.
(9) Oil pump outlet pressure limits for normal operation and idle, if oil tank is not part of the engine.
(10) Oil filter provisions and requirements.
1. Fuel system.
(1) Fuel, grade, type, and specification.
(2) Fuel inlet pressure limits.
(3) Fuel inlet temperature limits, where applicable, for external connection.
(4) Fuel return pressure limits.
(5) Inlet fuel flow rate.
(6) Method of preventing filter icing.
(7) Fuel filter provisions and requirements.
m. Maximum permissible exhaust attachment loads.
(1) Shear loads.
(2) Loads normal to mounting surfaces.
(3) Overhang moment.
5 June 1972 AC 33-2A Appendix 1
n. Bleed air attachment loads.
(1) Shear loads.
(2) Loads normal to mounting points.
(3) Overhang moment.
o. Accessory attachments. For each accessory drive, give the following information:
(1) Type of drive and mounting arrangement.
(2) Direction of rotation.
(3) Static torque (maximum limit).
(4) Continuous torque (limit).
(5) Drive shaft speed ratio with rotor or crankshaft.
(6) Maximum overhang moment.
(7) Vibration limits.
p. Output shaft. For turboprop or turboshaft engine.
(1) Maximum steady state allowable torque or power limits of the output shaft.
(2) Maximum allowable transient power output torque.
(3) Maximum bending load limits on the output shaft.
(4) The type and dimensions of the output shaft, direction of rotation, speed ratio with main rotor and nominal drive shaft speed.
Instrumentation. Describe all instrumentation provisions in detail. Describe provisions for connecting permanent and optional instrumentation including provisions for trend or conditions monitoring equipment.
External accessory units. List the function, model designation, setting numbers, or other pertinent identifying information relative to the following categories of major engine accessories, controls, and special equipment which comprise externally located separate assemblies or units:
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AC 33-2A 5 June 1972 Appendix 1
(2) Ignition system and subsystems.
(3) Propeller, air bleed, or anti-icing control units.
(4) Safety devices.
(5) Other engine accessories or components to be furnished as part of or with the engine.
(6) Optional aircraft or engine accessories available with the engine for mounting on or for use with the engine.
Performance data. Data should be presented in the form of suitable curves and tables, or should portray the relationship of the various parameters of a minimum engine of the model. Data covering the effects of varying ram pressure ratio, ambient temperature, air bleed and altitude should be provided, and the data basis indicated (e.g., estimated, test, minimum, mean, maximum).
C. Installation drawing. The applicant should provide an installation drawing of the engine showing all the dimensions and details necessary for proper installation of the engine in an aircraft.
u. Electronic radiation. The applicant should specify the maximum radiated electronic interference produced by the engine.
v • Operating and installation limitations. specify any additional information needed to describe adequately The applicant should the operational and installational limitations of the engine.
w. Electrical supply required. The applicant should specify the engine requirements for any externally supplied electricity.
x. Weight data.
(1) Dry weight of complete engine with all required equipment and no residual fuel or oil.
(2) Weights of optional external equipment and accessories.
(3) Estimated weight of residual fuel and lube oil.
(4) Center of gravity location of engine (dry).
5 June 1972 AC 33-2A Appendix 1
y. Mass monent of inertia of rotating system.
Estimated effective mass moment of inertia of those engine rotating components involved in starting when using the designated engine starting system.
(2) Estimated mass moment of inertia of main engine rotating component assemblies.
(3) Estimated effective mass moment of inertia of only the power turbine rotor (for a shaft power type engine).